1. Field of the Invention
The present invention relates mainly to a power supply apparatus, and in particular to a power supply apparatus for use in an image forming apparatus.
2. Description of the Related Art
In an image forming apparatus for performing image formation using an electrophotographic process, high voltages are used as a charging voltage, a transfer voltage, and a developing voltage. If such high voltages vary, the image density or the like will also vary. A variation in a resistive element or reference voltage needs to be corrected by adjusting an output voltage using a variable resistance when a high-voltage power supply is manufactured.
Meanwhile, Japanese Patent Laid-Open No. 2002-153062 discloses a power supply apparatus that includes a transformer as a factory default, in which a secondary side output of the transformer is detected, and the detected output value is stored in association with a duty value of a pulse width signal. After shipment from the factory, the power supply apparatus reads the duty value that is associated with a target output value from a storage device and uses the read duty value. Accordingly, adjustment using a variable resistance is not necessary.
According to Japanese Patent Laid-Open No. 2002-153062, a high output voltage can be corrected, but a variation in a reference voltage is not taken into consideration. In order to reduce an influence of the variation in a reference voltage that is to be supplied to the high-voltage power supply, a special IC that generates an accurate reference voltage is needed, causing an increase in manufacturing cost.